• 한국기계가공학회지
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• 제19권11호
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• pp.102-108
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• 2020

The demand for lightweight materials and high-strength steel has rapidly increased to help reduce the weight of a vehicle body; it improves the fuel efficiency of automobiles and provides passenger safety. Additionally, as the material becomes thinner, the demand for its resistance against corrosion becomes higher. Hence, the application of the surface-treated steel sheet has surged rapidly. In this study, a weld bonding experiment using a delta spot welding machine is performed on a thin sheet of a different material (Al6061-T6/GA440). The thickness of the material was kept at 1 mm to reduce the weight of the automobile body parts. Additionally, the purpose of this study is to control the heat input by applying the welding conditions of a multi-stage pressure pattern to improve corrosion resistance shear strength. The analysis of nugget diameter measurement, shear tensile test, and salt spray test was performed to achieve the aim.

• 한국분무공학회지
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• 제28권4호
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• pp.169-175
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• 2023

Multi-injection scheme is being applied to GDI combustion to reduce PM and PN emission to meet the EU7 regulation. However, very short injection duration encounters the ballistic injection region, which injection quantity does not increase linearly with injection duration when applying multi-injection. In this study, numerical studies were conducted to reveal the cause of ballistic injection and the effect of design parameters on ballistic region using 1-D simulation, AMESim. Injection rate and injection quantity were compared with experiment to validate the established model, which showed the accuracy with 10% error. The model revealed that the tendency of ballistic region coincides with the needle motion behavior, which means that parameters at the upper part of needle such as electro-magnetic force, needle spring force and needle friction force have dominant effect on ballistic injection. To figure out the effect of electro-magnetic and needle friction force on ballistic, those parameters were varied to plus and minus 10% with model. The result showed that those parameters clearly changed the ballistic region characteristics, however, the impact became insignificant for outside of ballistic region, which means that the ballistic injection is mainly influenced by initial motion of injector needle.

• 한국연소학회지
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• 제18권1호
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• pp.7-12
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• 2013

A quasidimensional program is developed for a four stroke cycle homogeneous GDI (Gasoline Direct Injection) engine. It includes models for spray, burning rate and chemistry to predict knock and emissions. With early injection a homogeneous GDI engine goes through spark ignited, turbulent premixed combustion as in PFI (Port Fuel Injection) engines. The cylinder charge is divided into unburned and burned zone with the latter divided into multiple zones of equal mass to resolve temperature stratification. Validation is performed against measured pressure traces, NOx and CO emissions at different load and RPM conditions. Comparison is made between an empirical knock model and predictions by the chemistry model in this work.

• 한국군사과학기술학회지
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• 제6권4호
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• pp.113-123
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• 2003

Both numerical analysis and experiment of cold and hot tests were performed to obtain basic design data for the swirl coaxial type Injector and to predict the combustion performance. Mass distribution, mixing distribution, mixing efficiency, characteristic velocity efficiency were measured by the cold tests and numerical analysis using the commercial thermo-hydraulic program. Test and analysis variables were recess, pressure drop, velocity ratio, mixing spray, mixture ratio. Hot tests were performed for the Uni-element injector to compare the performance with the cold test results, and, hot tests for Multi-element injector were performed to compare the performance with Uni-element injector. Designed thrust of the Uni-element injector liquid rocket was 35kgf at sea level and combustion chamber pressure, 20bar. Kerosene and Lox were used as a propellant.

• Journal of Korean Neurosurgical Society
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• 제37권4호
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• pp.303-306
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• 2005

In cases of brain or other organ abscess, the causative etiology or disease are not always definable. We report a case of brain, renal, and possibly lung abscesses in a middle aged woman. After close, stepwise surveillance of possible etiologic factors, we covered out a small solitary pulmonary arteriovenous fistula without any pulmonary symptoms and successfully occluded the fistula via endovascular approach. The congenital pulmonary arteriovenous fistula should be bear in mind as a cause of repeated, multiple systemic infective source spray and be pursued despite of negative initial baseline studies.

• 한국분무공학회지
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• 제8권1호
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• pp.1-8
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• 2003

The flow analysis of the axial fan of rotary burner was performed by SIMPLE(Semi Implicit Method for Pressure Linked Equations) algorithm and finite volume mothod performed in the case of 3-D, incompressible, turbulent flow. In this study, the coordinate transformation was adapted for the complex geometry of axial fan, and the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent flow. Multi-block grid system was used for flow field and divided into four domains such as the inlet, outlet, flow field of rotating vane, and tip clearance. Fan rotation was simulated by rotational motion using MRF(Multiple Rotating Reference Frame) in steady, incompressible state flow.

• 한국전자통신학회논문지
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• 제8권2호
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• pp.279-284
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• 2013

본 논문에서는 경제적이고, 채널 확장성이 용이하며, 다양한 성능시험에 대응이 가능한 솔레노이드 타입의 인젝터 컨트롤러를 연구 개발하고 그 성능을 평가하였다. 개발된 컨트롤러는 임베디드 시스템에 기반을 두고 있으며, 인젝터에서 고압으로 분사되는 연료의 분사 타이밍 및 분사량에 대한 정밀제어는 물론 솔레노이드의 전기적인 특성을 측정하여 인젝터의 성능평가도 가능하다. 또한, 부가적으로 인젝터의 분무 형태를 정밀하게 촬영할 수 있는 광원과 초고속 카메라의 정밀시간제어도 동시에 가능하도록 하였다.

• 한국분무공학회지
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• 제18권2호
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• pp.94-99
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• 2013

The spherically-symmetric burning of an isolated droplet is a dynamic problem that involves the coupling of chemical reactions and multi-phase flow with phase change. For the improved understanding of these phenomena, this paper presents the numerical results on the n-heptane droplet combustion conducted at a 1 atm ambient pressure in three different initial droplet diameter ($d_0$). The main purpose of this study is to provide basic information of droplet burning, extinction and flame behavior of n-heptane and improve the ability of theoretical prediction of these phenomena. To achieve these, the numerical analysis was conducted in terms of normalized droplet diameter ($d/d_0$), flame diameter ($d_f$) and flame standoff ratio (FSR) under the assumptions that the droplet combustion can be described by both the quasi-steady behavior for the region between the droplet surface and the flame interface and the transient behavior for the region between the flame interface and ambient surrounding.

• 한국자동차공학회논문집
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• 제8권1호
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• pp.40-47
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• 2000

A model for the prediction of combustion and exhaust emissions of DI diesel engine has been formulated and developed. This model is a quasi-dimensional phenomenological one and is based on multi-zone combustion modelling concept. This model is developed based on the concept of Hiroyasu's multizone combustion models. It takes nozzle injection (spray) parameters, induction swirl into consideration and the models of zone velocity, air entrainment, fuel droplet evaporation and mixture combustion are upgraded. Various parameters, such as cylinder pressure, heat release rate, Nox and soot emission, and these parameters in the zone are simulated. The results are compared with the experimental ones, too.

• 마이크로전자및패키징학회지
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• 제26권4호
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• pp.107-111
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• 2019

We report the fabrication of a CdS/CuInGaSe (CdS/CIGS) structure with carbon nanotubes and its application as a photocathode for photoelectrochemical water splitting. CIGS thin films were fabricated using co-evaporation by RF magnetron sputtering, while CdS was fabricated by chemical bath deposition. Spray coated multi-wall carbon nanotube (CNT) film on CdS/CIGS thin film was investigated as a photocathode. The CNT-coated CdS/CIGS showed superior photocurrent density and exhibited improved photostability.